package network;
//    服务器


import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {

    private DatagramSocket socket = null;

    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动!");
        while (true) {
            //读取请求并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            //为了方便在Java代码中处理(尤其是后面的打印)可以把上诉数据报中的二进制数据,拿出来,构造成String
            String request = new String(requestPacket.getData(),0,requestPacket.getLength());
            //2)根据请求计算相应
            String response = this.process(request);
            //3)把响应写回客户端
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),0,response.getBytes().length,
                    requestPacket.getSocketAddress());
            socket.send(responsePacket);
            System.out.printf("[%s:%d] req = %s, resp = %s\n",requestPacket.getAddress(),requestPacket.getPort(),request,response);
        }
    }

    //由于当前是回响服务器
    public String process(String request) {
        return request;
    }
    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(9090);
        server.start();
    }
}
